Dispersion Reagent Research Articles

Повышение селективности модифицирования спектральных характеристик алмазов перед процессом рентгенолюминесцентной сепарации

Introduction. A promising direction in solving the problem of increasing the recovery of diamonds with weak or anomalous luminescence is the use of modern technologies for modifying the spectral characteristics of diamonds with luminophore-containing reagents. Materials and methods. In the experiments, we used collections consisting of diamond crystals with weak and anomalous luminosity and grains of kimberlite minerals selected from the gravity enrichment concentrate. When evaluating the efficiency of fixing luminophores on the surface of diamonds, a vision-metric method was used in UV radiation with the determination of the proportion of surface areas covered with luminophores. The spectral and kinetic characteristics of diamond crystals and kimberlite grains were measured under laboratory conditions on a «Polus-M» separator. The separation of diamonds and kimberlite grains was carried out in the mode used in the industrial radar process. Results. The causes and regularities of the interaction of modifier reagents with kimberlite minerals, as well as the effect of dispersant reagents on the fixation of luminophores and the spectral and kinetic characteristics of kimberlite are determined. Discussion. It is shown that the fixation of an organic collector with luminophores on kimberlite minerals proceeds according to the adhesion mechanism with the formation of focal surface formations on hydrophobic minerals and point fixation on the surface of faces with low surface energy. It is shown that the high selectivity of the X-ray luminescence separation process is achieved at a surface concentration of the luminophores on diamonds of at least 15 % and a surface concentration of luminophores on kimberlite minerals of no more than 3%, controlled by the addition of reagents-dispersants. Conclusions. The article presents the results of studies of the mechanism and regularities of fixing luminophore-containing compositions on kimberlitic minerals in the presence of dispersant reagents. It was found that the addition of luminophore-containing reagents-modifiers of sodium hexametaphosphate, sulfonol, carboxymethylcellulose and liquid glass to the aqueous phase of emulsions provides an increase in the selectivity of fixing luminophores on the surface of diamonds and improves the performance of X-ray luminescent separation of diamond-containing products. A mode of increasing the selectivity of the action of an aqueous emulsion of the MLA-3 modifier reagent based on luminophore E-515-115-G5 has been developed by adding sodium hexametaphosphate to the emulsion aqueous phase at a concentration of 1-1.5 g/l, providing 90% recovery of weakly and abnormally luminous diamonds into the X-ray luminescent separation concentrate with a decrease in kimberlite yield by 33 %. The tested modifier agents and the selected conditions of their application can be useful in industrial conditions for the X-ray luminescent separation of diamond-containing kimberlites. Resume. As a result of the studies, a mode was developed to increase the selectivity of the action of an aqueous emulsion of the MLA-3 modifier reagent based on the E-515-115-G5 luminophore with the addition of a dispersant reagent (sodium hexametaphosphate) to the aqueous phase of the emulsion at a concentration of 1-1.5 g/l , providing the possibility of 90 % extraction of weakly and abnormally luminous diamonds into the concentrate of X-ray luminescent separation while reducing the yield of kimberlite by 33 %. Suggestions for practical application and direction for future research. The developed reagents-modifiers and the selected conditions for their use are recommended for testing and implementation in industrial conditions.

Ultrasensitive Mg2+-Modulated Carbon Nanotube/Tannic Acid Aerogels for High-Performance Wearable Pressure Sensors

Three-dimensional (3D) carbon nanotube-based porous networks have received considerable attention as active nanomaterials for flexible/wearable sensor applications due to their excellent conductivity and mechanical flexibility. Herein, ultralight, biocompatible, and conductive SWCNT/tannic acid (TA) and Mg2+/SWCNT/TA aerogels have been facilely fabricated using TA as a dispersion reagent and crosslinker and Mg2+ to introduce a metal–phenolic network. The construction of a SWCNT@TA core–shell structure and the low CNT concentration of SWCNT/TA3:3 contribute to a high linear sensitivity of 432 kPa–1 in a wide pressure range (0.014–28 kPa), while Mg2+ modulation endows Mg2+/SWCNT/TA1:1 with an ultrahigh linear sensitivity of 13662 kPa–1 in a pressure range of 0.014–1.05 kPa. The superior sensing performance of as-prepared aerogels, including high sensitivity, wide working range, low detection limit (14 Pa), and fast stimuli-response (200–300 ms), enables them to detect tiny changes in human biosignals and imperceptible vibration, which show great potential in applications of health monitoring, human–machine interfaces, and various flexible electronics.

Carbon nanoparticles suspension injection for photothermal therapy of xenografted human thyroid carcinoma in vivo.

Due to the unique structure, carbon nanomaterials could convert near‐infrared (NIR) light into heat efficiently in tumor ablation using photothermal therapy (PTT). Carbon nanoparticles suspension injection (CNSI) is a commercial imaging reagent for lymph node mapping. CNSI has similar structural characteristics to other carbon nanomaterials, and thus, might be applied as photothermal agent. Herein, we evaluated the photothermal conversion ability and therapeutic effects of CNSI on thyroid carcinoma. CNSI was composed by carbon nanoparticle cores and polyvinylpyrrolidone K30 as the dispersion reagent. CNSI absorbed NIR light efficiently following the Lambert‐Beer law. The temperature of CNSI dispersion increased quickly under the NIR irradiation. CNSI killed the TCP‐1 thyroid carcinoma cells under 808 nm laser irradiation at 0.5 W/cm2, while CNSI or NIR irradiation treatment alone did not demonstrate this effect. Temperature increases were observed in tumor injected with CNSI under NIR irradiation. After three irradiation treatments, the tumor growth was completely blocked and the disruption of cellular structure was observed. When the tumor temperatures reached 53°C during treatment, the tumors did not recur within the observation period of 3 months. Our results suggested that CNSI might be used for PTT through “off label” use to benefit the patients immediately.

Nanoengineering of uniform and monodisperse mesoporous carbon nanospheres mediated by long hydrophilic chains of triblock copolymers

A one-step soft templating strategy for synthesizing uniform and monodisperse mesoporous carbon nanospheres (UM-MCNs) with sub-100 nm size and large mesopores without using any co-solvent additives has not yet been reported. Herein, an extremely simple,effective and environment friendly strategy was first developed to prepare uniform, monodisperse polymer nanospheres (PNs) and UM-MCNs with small particle size (80–90 nm) and large mesopores (~ 6.8 nm), where F108 with long hydrophilic chains not only served as mesopore-forming reagent, but also as a dispersant reagent that facilitated uniform growth of the nanospheres, resulting in a narrow particle size distribution. Moreover, F108 could also act as a stability-driving agent, that is, the phloroglucinol/formaldehyde polymer was tightly “locked” by the long hydrophilic segments of F108 via strong hydrogen bonding. Consequently, intact carbon nanospheres with large mesopores were obtained after carbonization, and finally a three-dimensional periodic arrangement of the UM-MCNs was formed. In addition, ethanol could be used as a co-surfactant or co-solvent during self-assembly. The present strategy may not only supply a novel avenue to synthesize UM-MCNs, but also shed light on insights into the profound impact of F108 with long hydrophilic chains and ethanol on the morphology and pore size of carbon spheres.

Adsorption properties and mechanism of purified palygorskite on methylene blue

The palygorskite clay minerals from Gansu Province in China were purified by suspension precipitation method using sodium hexametaphosphate solution as dispersion reagent. The content of quartz and dolomite associated minerals in palygorskite clay minerals reduced effectively after purification, as confirmed by X-ray diffraction (XRD), infrared spectra (IR), scanning electron microscope (SEM), and energy-dispersive spectroscopy (EDS) analyses. The purified palygorskite exhibits excellent adsorption capacity for methylene blue (MB) in water, with the maximum adsorption capacity of 219.69 mg g−1. The adsorption kinetic studies revealed that adsorption kinetic of palygorskite on MB followed pseudo-second-order model. The adsorption mechanism of palygorskite for MB was discussed in detail via zeta potential analysis, N2 adsorption desorption curve and BET analysis, and infrared absorption spectrum analysis. The results demonstrated that the adsorption mechanism may be attributed to electrostatic interaction between MB and the negative charge on the palygorskite surface. Meanwhile, the bond M-OH in palygorskite structure can combine with N, S element in MB to form intermolecular hydrogen bonds.

Study on the pre-treatment of oxidized zinc ore prior to flotation

The pre-treatment of zinc oxide bearing ores with high slime content is important to ensure that resources are utilized optimally. This paper reports an improved process using hydrocyclone de-sliming, dispersion reagents, and magnetic removal of iron minerals for the pre-treatment of zinc oxide ore with a high slime and iron content, and the benefits compared to traditional technologies are shown. In addition, this paper investigates the damage related to fine slime and iron during zinc oxide flotation, the necessity of using hydrocyclone de-sliming together with dispersion reagents to alleviate the influence of slime, and interactions among hydrocyclone de-sliming, reagent dispersion, and magnetic iron removal. Results show that under optimized operating conditions the entire beneficiation technology results in a flotation concentrate with a Zn grade of 34.66% and a recovery of 73.41%.

Selective Dispersion of Large‐Diameter Semiconducting Carbon Nanotubes by Functionalized Conjugated Dendritic Oligothiophenes for Use in Printed Thin Film Transistors

AbstractSelective dispersion of semiconducting single walled carbon nanotubes (s‐SWCNTs) by conjugated polymer wrapping is recognized as the most promising scalable method for s‐SWCNT separation. Despite a number of linear conjugated polymers being reported for use in s‐SWCNT separation, these linear polymers suffer batch‐to‐batch variation for their undefined molecular structure. Here, it is reported that conjugated dendritic oligothiophenes with multiple diketopyrrolopyrrole groups at the periphery have the capability of selectively dispersing large diameter s‐SWCNTs with high dispersion efficiency and certain chiral selectivity. Printed top‐gated thin film transistors using the dendrimer sorted s‐SWCNTs show high charge carrier mobility of up to 57 cm2 V−1 s−1 and on/off ratios of ≈106 with high reproducibility, which is ascribed to the defined and monodispersed molecular structure of dendrimers. Moreover, owing to the multiple peripheral anchoring groups of these dendritic molecules, these dendrimer‐s‐SWCNT dispersions display excellent stability. The current work proves that dendritic molecules are excellent dispersion reagents for s‐SWCNT separation.

Evaluating a sodium dispersion reagent for the Bouveault-Blanc reduction of esters.

A new sodium dispersion reagent has been evaluated for the reduction of esters. Na-D15, a sodium dispersion with sodium particle size of 5-15 μm, is a nonpyrophoric reagent that can be handled in air. In this study, a broad range of aliphatic ester substrates were reduced to primary alcohols by Na-D15/i-PrOH with good yields. The method compares favorably with modern metal hydride reductions and is much safer and efficient than the traditional Bouveault-Blanc reduction.

Exploration on structure and stability of polypropylene during heating and cooling processes in terms of molecular dynamics simulations

Polymer materials are widely applied as drug solid dispersion reagents. The exploration and investigation on the structure and stability of different phases of polypropylene (PP) are very important and challenging, which will be very helpful for understanding of the reason why drug solid dispersion reagents can stabilize the drugs. In this work, the structure, thermodynamic and kinetic behaviors of PP polymers with different chain length during heating and cooling processes are examined and investigated based on molecular dynamics simulations. The simulated glass transition temperatures of the PP polymers are in agreement with experimental values. The amorphous PP1000–PP3000 exhibit higher stability than their crystalline states, but it is not the case for PP4000. Results reveal that the two important factors, that is, large entropy and relatively low molecular mobility lead to the high stability of amorphous PP1000–PP3000.

Some Insight into Stability of Amorphous Poly(ethylene glycol) Dimethyl Ether Polymers Based on Molecular Dynamics Simulations.

Poly(ethylene glycol) dimethyl ether (PEGDME) polymers are widely used as drug solid dispersion reagents. They can cause the amorphization of drugs and improve their solubility, stability, and bioavailability. However, the mechanism about why amorphous PEGDME 2000 polymer is highly stable is unclear so far. Molecular dynamics (MD) simulation is a unique key technique to solve it. In the current work, we systematically investigate structure, aggregate state, and thermodynamic and kinetic behaviors during the phase-transition processes of the PEGDME polymers with different polymerization degree in terms of MD simulations. The melting and glass-transition temperatures of the polymers are in good agreement with experimental values. The amorphous PEGDME2000 exhibits high stability, which is consistent with the recent experiment results and can be ascribed to a combination of two factors, that is, a high thermodynamic driving force for amorphization and a relatively low molecular mobility.

Study on modification of Cu-based oxygen carrier for chemical looping combustion

Chemical looping combustion (CLC) is a promising technology for segregation of carbon dioxide. CLC uses a metal oxide as an oxygen carrier, which transfers oxygen from the air to the fuel avoiding direct contact between them, thus separating the carbon dioxide and nitrogen. Cu-based oxygen carriers are excellent mediums due to high reactivity, environmental friendliness, and favorable thermodynamics. However, there are agglomeration issues due to low melting point of Cu. To solve this issue, a new preparation method as well as a dispersion reagent and a thermal durability-enhanced reagent were applied simultaneously to the oxygen carrier. The carriers were synthesized using both wet and dry impregnation methods. Based on the initial oxygen loading capability tests, the dry impregnation method received additional investigation. The characterizations of the oxygen carriers were evaluated using thermogravimetric analyzer (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), and surface area analyzer. TG results demonstrate that the enhanced dry impregnation was an effective preparation method, where the mass loss of the oxygen carrier was typically 3.4 %, correlating to almost 17 % loaded CuO. XRD results indicate a new phase, CuAl2O4 spinel, formed after the first few redox cycles, which is responsible for promoting the thermal stability of the oxygen carriers. SEM results show that the addition of the dispersants decreased the agglomeration and the enhanced reagent chemicals greatly improved the strength of the carriers. However, the surface area of the oxygen carriers decreased with the addition of the additives. In addition, with the increasing redox cycles, the surface area also decreased while the pore size increased, indicating that small pores were crushed, but the reactivity of the oxygen carriers did not decrease. In conclusion, the oxygen carriers produced in this manner are suitable for multi-cycle tests, and a major hurdle toward reducing greenhouse gases has been achieved.

Superstrate CuInS2 Photovoltaics with Enhanced Performance Using a CdS/ZnO Nanorod Array

An air-stable, low-temperature, solution-based process for preparing CuInS(2) (CIS) superstrate solar cells using CdS-decorated ZnO nanorod (NR) arrays is reported. Efficient light harvesting and photoexcited charge transport were achieved by fabricating a ZnO NR window layer with a large p-n junction area via a hydrothermal reaction. A CdS buffer layer was deposited on a transparent ZnO NR substrate at room temperature via successive ion layer adsorption and reaction (SILAR) or nanocrystal layer deposition (NCLD). The prepared CdS/ZnO NR assembly was coated with a CIS absorber layer without the need for surface passivation organics or dispersion reagents. The CIS precursor solution, prepared using a metal salt, thiourea, and an amine solvent, yielded CIS nanocrystals (NCs) at temperatures up to 250 °C. The CIS/CdS/ZnO NR heterojunction structure exhibited an excellent photovoltaic performance compared to a planar ZnO film device due to enhanced light transmittance toward the absorber and a high charge collection efficiency. These results suggest that a superstrate CIS/CdS/ZnO NRs photovoltaic cell fabricated via the low-cost route described here has great potential as a next-generation solar cell device.

Synthesis of polyaniline nanofibers with high electrical conductivity from CTAB–SDBS mixed surfactants

Mixed surfactant solution, containing cetyltrimethyl ammonium bromide (CTAB) and sodium dodecylbenzyl sulfonate (SDBS), is used to prepare polyaniline (PANI) with soft 1D structure and high electrical conductivity. The mixed surfactants in the reaction play double roles of soft templates and dispersion reagents. The influence of CTAB–SDBS ratio on the morphology and conductive property of PANI is investigated. Through varying the proportion of surfactants, uniformly branched nanofibers with higher aspect ratio and good dispersion are obtained, which possess the highest conductivity (0.102 S·cm −1). Moreover, FT-IR spectra are measured to explain the change of structure and conductivity under assistance of mixed surfactants. As a result, the mixed surfactants have significant effect on the electron density of whole structure as well as the PANI molecular orientation.

Determination of chloropropanols in foods by one-step extraction and derivatization using pressurized liquid extraction and gas chromatography–mass spectrometry

3-Chloropropane-1,2-diol (3-MCPD) and 1,3-dichloro-2-propanol (1,3-DCP) were determined for the first time in bakery foods using pressurized liquid extraction (PLE) combined with in situ derivatization and GC–MS analysis. This one-step protocol uses N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) as silylation reagent. Initially, screening experimental design was applied to evaluate the effects of the variables potentially affecting the extraction process, namely extraction time (min) and temperature (°C), number of cycles, dispersant reagent (diatomaceous earth in powder form and as particulate matter with high pore volume Extrelut NT) and percent of flush ethyl acetate volume (%). To reduce the time of analysis and improve the sensitivity, derivatization of the compounds was performed in the cell extraction. Conditions, such as the volume of BSTFA, temperature and time for the in situ derivatization of analytes using PLE, were optimized by a screening design followed to a Doehlert response surface design. The effect of the in-cell dispersants/adsorbents with diatomaceous earth, Florisil and sodium sulfate anhydrous was investigated using a Box–Behnken design. Using the final best conditions, 1 g of sample dispersed with 0.1 g of sodium sulfate anhydrous and 2.5 g diatomaceous earth was extracted with ethyl acetate. 1 g of Florisil, as clean-up adsorbent, and 70 μL of BSTFA were used for 3 min at 70 °C. Under the optimum conditions, the calibration curves showed good linearity ( R 2 > 0.9994) and precision (relative standard deviation, RSD ≤ 2.4%) within the tested ranges. The limits of quantification for 1,3-DCP and 3-MCDP, 1.6 and 1.7 μg kg −1, respectively, are far below the established limits in the European and American legislations. The accuracy, precision, linearity, and limits of quantification provided make this analytical method suitable for routine control. The method was applied to the analysis of several toasted bread, snacks, cookies and cereal samples, none of which contained chloropropanols at concentrations above the legislation levels.

PEG-6000 Assisted Growth of Copper Dendrites

Highly uniform copper dendrites were successfully prepared in large quantities by a simple wet chemical approach using hydrazine hydrate as reducant in the presence of polyethylene glycol 6000 (PEG-6000) at room temperature. Scanning electron microscopy (SEM), ultraviolet (UV)-vis absorption spectroscopy, and x-ray diffraction (XRD) have been used to characterize the obtained products. It is found that the architecture of copper particles is drastically influenced by the mass ratio of PEG-6000/CuSO4(aq), PEG-6000/N2H4 · H2O, CuSO4(aq)/N2H4 · H2O and the concentration of precursors. It is revealed that PEG-6000 might play both capping reagent and dispersion reagent roles.

Effects of Process Conditions on Properties of Nanoscale Organic Pigment Encapsulated by Poly(styrene-maleic acid) Dispersion

The effects of process conditions on properties of nanoscale organic pigment red 122 encapsulated by poly(styrene-maleic acid) dispersion were evaluated. The results revealed that sodium hydroxide provided the dispersion superior performance as compared with other additives, regardless of it being taken as dispersant or hydrolysis reagent. An optimal process was attained by using sodium hydroxide with a dosage of 0.6–0.68 times of molar amount of ‒COOH groups in poly(styrene-maleic acid) when the pigment/poly(styrene-maleic acid) was hydrolyzed at 45°C for 30 minutes.

Growth of Dendritic Silver Crystals in CTAB/SDBS Mixed-Surfactant Solutions

Novel dendritic silver crystals, which consist of several branches with lengths up to 10 μm, have been successfully synthesized by a simple wet chemical route using l-ascorbic acid as reductant in cetyltrimethylammonium bromide (CTAB) and sodium dodecyl benzyl sulfonate (SDBS) mixed surfactant solution at room temperature. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and UV−vis absorption spectroscopy have been used to characterize the obtained silver products. It is found that the architecture of silver crystals is drastically influenced by the molar ratio, concentration of CTAB/SDBS, and the concentration of the precursors. It is revealed that the mixed-surfactant solution might play both capping reagent and dispersion reagent roles.

Effect of Dispersant on the Particle Size Distribution of Cu Powders Prepared by Wet-Reduction Process

Monodispersed Cu powders were prepared in aqueous solution through a wet-reduction process with hydrazine hydrate (N2H4·H2O). In particular, the effect of the dispersant such as sodium pyrophosphate decahydrate (Na4O7P2·10H2O), carboxymethyl cellulose sodium salt (CMC) in water solvent on the particle size for the prepared Cu powders was investigated. The Cu powders essentially were monodispersed and irregular in shape regardless of reaction temperature and dispersant. In the case of adding the Na4O7P2·10H2O, the particle size of Cu powders increased with the increase of reaction temperature, which the particles were agglomerated in irregular shape and became to be large. The particle size distributions was asymmetry and to be broad regardless of reaction temperature. On the other hand, when the CMC was added, the particle size of Cu powders, which were much finer compared with adding the Na4O7P2·10H2O as a dispersant, was not much changed with reaction temperature. The particle size distribution of Cu powder was much narrow regardless of reaction temperature. As a result, it would be suggested that the CMC was more effective dispersant reagent to produce the monodispersed and fine Cu powders with narrow size distribution using the wet chemical reduction process

Preparation of lithium fast ionic conductor by sol-gel-hydrothermal method

The solid fast ionic conductor was synthesized by the sol-gel-hydrothermal method. The influences of the dispersion reagent, the alkalinity and the calcination temperature on the surface morphology of nanopowders, and the electric conductivity were discussed. When PEG 12000 was used as the dispersion reagent, the alkalinity was 1.0% and the calcination temperature was 550°C; the electric conductivity at ambience temperature of the inorganic nanopowder of lithium fast ionic conductor synthesized was 2.59 × 10−3 S·cm−1.

Monitoring stability of reaction and dispersion states in a suspension polymerization reactor using electrical resistance tomography measurements

A system was constructed for visualizing the dispersion states of liquid monomer and polymer droplets in a suspension polymerization reaction in a non-intrusive and continuous manner using electrical resistance tomography measurements. Using this system, a method was established for keeping reaction states stable and the quality of the particles produced good by varying the mixing conditions, such as the rotational speed of the impeller and the injection amount of dispersion reagents, under the principles that the lower the rotational speed of the impeller, the better; and the smaller the injection amount of dispersing agents, the better. It was found that the amount of additional injection significantly affected both the sharpness and the average value of the particle diameter distribution, based on the data of the tomograms.